اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدTesting bound dark energy with cosmological parameter and fundamental constant evolution
64
0
0.0
(
0
)
تأليف
Rodger I. Thompson
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
A new bound dark energy, BDE, cosmology has been proposed where the dark energy is the binding energy between light meson fields that condense a few tens of years after the big bang. It is reported that the correct dark energy density emerges using particle physics without fine tuning. This alone makes the BDE cosmology worthy of further investigation. This work looks at the late time BDE predictions of the evolution of cosmological parameters and the values of fundamental constants to determine whether the cosmologys predictions are consistent with observation. The work considers the time period between a scale factor of 0.1 and 1.0. A model BDE cosmology is considered with current day values of the cosmological parameters well within the observational limits. The calculations use three different values of the current day dark energy equation of state close to minus one. All three cases produce evolutions of the cosmological parameters and fundamental constants consistent with the observational constraints. Analytic relations between the BDE and cosmological parameters are developed to insure a consistent set of parameters.
قيم البحث
اقرأ أيضاً
Phantom dark energy can produce amplified cosmic acceleration at late times, thus increasing the value of $H_0$ favored by CMB data and releasing the tension with local measurements of $H_0$. We show that the best fit value of $H_0$ in the context of
the CMB power spectrum is degenerate with a constant equation of state parameter $w$, in accordance with the approximate effective linear equation $H_0 + 30.93; w - 36.47 = 0$ ($H_0$ in $km ; sec^{-1} ; Mpc^{-1}$). This equation is derived by assuming that both $Omega_{0 rm m}h^2$ and $d_A=int_0^{z_{rec}}frac{dz}{H(z)}$ remain constant (for invariant CMB spectrum) and equal to their best fit Planck/$Lambda$CDM values as $H_0$, $Omega_{0 rm m}$ and $w$ vary. For $w=-1$, this linear degeneracy equation leads to the best fit $H_0=67.4 ; km ; sec^{-1} ; Mpc^{-1}$ as expected. For $w=-1.22$ the corresponding predicted CMB best fit Hubble constant is $H_0=74 ; km ; sec^{-1} ; Mpc^{-1}$ which is identical with the value obtained by local distance ladder measurements while the best fit matter density parameter is predicted to decrease since $Omega_{0 rm m}h^2$ is fixed. We verify the above $H_0-w$ degeneracy equation by fitting a $w$CDM model with fixed values of $w$ to the Planck TT spectrum showing also that the quality of fit ($chi^2$) is similar to that of $Lambda$CDM. However, when including SnIa, BAO or growth data the quality of fit becomes worse than $Lambda$CDM when $w< -1$. Finally, we generalize the $H_0-w(z)$ degeneracy equation for $w(z)=w_0+w_1; z/(1+z)$ and identify analytically the full $w_0-w_1$ parameter region that leads to a best fit $H_0=74; km ; sec^{-1} ; Mpc^{-1}$ in the context of the Planck CMB spectrum. This exploitation of $H_0-w(z)$ degeneracy can lead to immediate identification of all parameter values of a given $w(z)$ parametrization that can potentially resolve the $H_0$ tension.
Under the assumption that the variations of parameters of nature and the current acceleration of the universe are related and governed by the evolution of a single scalar field, we show how information can be obtained on the nature of dark energy fro
m observational detection of (or constraints on) cosmological variations of the fine structure constant and the proton-to-electron mass ratio. We also comment on the current observational status, and on the prospects for improvements with future spectrographs such as ESPRESSO and CODEX.
We have detected narrow HI 21cm and CI absorption at $z sim 1.4 - 1.6$ towards Q0458$-$020 and Q2337$-$011, and use these lines to test for possible changes in the fine structure constant $alpha$, the proton-electron mass ratio $mu$, and the proton g
yromagnetic ratio $g_p$. A comparison between the HI 21cm and CI line redshifts yields $Delta X/X = [+6.8 pm 1.0] times 10^{-6}$ over $0 < <z> le 1.46$, where $X = g_p alpha^2/mu$, and the errors are purely statistical, from the gaussian fits. The simple line profiles and the high sensitivity of the spectra imply that statistical errors in this comparison are an order of magnitude lower than in previous studies. Further, the CI lines arise in cold neutral gas that also gives rise to HI 21cm absorption, and both background quasars are core-dominated, reducing the likelihood of systematic errors due to local velocity offsets between the hyperfine and resonance lines. The dominant source of systematic error lies in the absolute wavelength calibration of the optical spectra, which appears uncertain to $sim 2$ km/s, yielding a maximum error in $Delta X/X$ of $sim 6.7 times 10^{-6}$. Including this, we obtain $Delta X/X = [+6.8 pm 1.0 (statistical) pm 6.7 (max. systematic)] times 10^{-6}$ over $0 < <z> le 1.46$. Using literature constraints on $Delta mu/mu$, this is inconsistent with claims of a smaller value of $alpha$ from the many-multiplet method, unless fractional changes in $g_p$ are larger than those in $alpha$ and $mu$.
We discuss the existence of an acceleration scale in galaxies and galaxy clusters. The presence of the same acceleration scale found at very different scales and in very different astrophysical objects strongly supports the existence of a fundamental
acceleration scale governing the observed gravitational physics. We also comment on the implication of such a fundamental acceleration scale on the problem of dark matter. We discuss the relevance of the fundamental acceleration for the nature of dark matter as well as for structure formation to be explored in future numerical simulations.
We report Westerbork Synthesis Radio Telescope and Arecibo Telescope observations of the redshifted satellite OH-18cm lines at $z sim 0.247$ towards PKS1413+135. The conjugate nature of these lines, with one line in emission and the other in absorpti
on, but with the same shape, implies that the lines arise in the same gas. The satellite OH-18cm line frequencies also have different dependences on the fine structure constant $alpha$, the proton-electron mass ratio $mu = m_p/m_e$, and the proton gyromagnetic ratio $g_p$. Comparisons between the satellite line redshifts in conjugate systems can hence be used to probe changes in $alpha$, $mu$, and $g_p$, with few systematic effects. The technique yields the expected null result when applied to Cen.A, a nearby conjugate satellite system. For the $z sim 0.247$ system towards PKS1413+135, we find, on combining results from the two telescopes, that $[Delta G/G] = (-1.18 pm 0.46) times 10^{-5}$ (weighted mean), where $G = g_p [mu alpha^2]^{1.85}$; this is tentative evidence (with $2.6 sigma$ significance, or at 99.1% confidence) for a smaller value of $alpha$, $mu$, and/or $g_p$ at z~0.247, i.e. at a lookback time of ~2.9 Gyrs. If we assume that the dominant change is in $alpha$, this implies $[Delta alpha /alpha ] = (-3.1 pm 1.2) times 10^{-6}$. We find no evidence that the observed offset might be produced by systematic effects, either due to observational or analysis procedures, or local conditions in the molecular cloud.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
